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No, you will not report CESB as a capital gain, you will report it as other income on line 13000 of your tax return.
As per CRA, add up each COVID-19 benefit payment amount you received from your T4A slip and enter the total amount on line 13000 of your tax return.
Please see our TurboTax article on Canada Emergency Student Benefit (CESB) to learn more about CESB and tax implications.